Nudging them to get things done is to be expected for many employees - it is considered good management practice by many. They are employees, not founders, and you should expect them to need some nudging - the solution is to develop processes to give them the nudging they need to make them worth what you pay them to you.

I'd suggest calling all 8 for 5-10 minutes a day (it's less than an hour of work - if you don't have time for that, appoint someone else with the skills as manager). Ask them for a brief verbal description of how they are going, what problems they are facing, and what worked. Make it mainly positive - praise them for what they have done, guide them on what needs to be done, and if needed, gently reprimand them if something isn't so good. Keep it short and focus on the needs of the business and give them autonomy when possible, unless they need more help.

If you find that, even when properly managed as above, performance means they are not worth what you pay them, schedule an in-person meeting or if that is impossible, a call. Tell them their continued employment is at risk, and let them bring a representative if they want. Make sure you observe all employment law and contract terms applicable to you. At the meeting, explain that their current performance is making them a drag on the business, and explain exactly why. Give them plenty of time to explain themselves. Then, ask them how they can improve their performance. Set achievable milestones at the meeting for them to step up their performance to a reasonable level that everyone is happy with. For coders, that could be a list of tasks to finish, with times they will finish them by. Ask them if there is anything you can do to help them improve - and if it is reasonable, do it.

If they don't meet the performance targets, and don't have a good enough reason, then you can think about dismissal (in accordance with their contract terms and applicable employment law).

Dismissing so many people is going to kill morale at your startup - if it looks like you have to, you might be better off trying to start a new one, sell assets to the new one, hire the good ones, and wind up the first startup making everyone redundant (to the extent that is legally possible). If the first startup is financially solvent, you can sell assets (e.g. your codebase, trademarks etc...) to the new one.

If you do hire people, the most important thing is to get someone who knows the field the potential hiree is in to assist with the interviewing. Ignore bits of paper like qualifications or resumes, except to screen out candidates who don't even claim skills you need. Don't believe anything in a CV or that any qualification means they know anything you need - ask them to solve a task that would take a good employee an hour for you, and rate their work. Also look for experience that is actually proven - working in a team for a big company doesn't prove much, even with references. Look for good quality Free / Open Source code (actually look through the revision history, and check the quality of their commits), or successful projects where they were obviously behind it (a history of consulting as sole programmer on different successful jobs for one business could be good evidence).