Urea nitrogen isn't absorbed by the leaves, and may cause build-up of fertilizer salts. Too much nitrogen can boost foliage growth, often at the expense of form and color. Organic fertilizers may also be used. The 1977 edition of Bromeliads - A Cultural Handbook from the BSI recommends a brew made of sheep manure and water. A discussion of fertilizers on the BSI Round Robin dealt with use of fish emulsion.
High nitrogen is probably the main culprit.
As mentioned above, these two genera are very susceptible to the effects of overfeeding. They should be fed sparingly - if at all. Others suggest not fertilizing either of these genera at all. The plants will be smaller, but should have good color and conformation.