and there he is...
This phenomenon is called "alligatoring" or "elephant skin".
It is caused by the first layer of gelcoat not being cured properly. This can be caused by:
-temperature
-under catalisation (too little MEKP added. Check the datasheets, usually 2%)
-improper mixing
-too little cobalt added (should not be the problem, in non-tropical countries cobalt is added to gelcoats as standard)
As soon as the second layer (gelcoat or laminate) hits the first layer, the first layer cannot cope with the high styrene levels and starts to "live" causing these wrinkles.
Nothing to really worry about, but it does give you some nice hours of refairing and painting...