Xenotoca, cyanobacteria, deformities ...

After all the talk on deformities I like to bring up the subject yet again. For some time I had Xenotoca "San Marcos" together with Ameca splendens. Both species were reproducing, and since both were together, they were housed in the same conditions. After some struggles with food-quality (see old messages), I did not note any deformities for a long time in either species. In a second aquarium I had some Characodon, and for some time I housed a group of juvenile Xenotoca with these. About half of these Xenotoca suffered a peculiar deformity: at birth they were fine but while growing up their vertebral column became s-shaped in the vertical direction with the tail standing upwards. More recently I started keeping also the adult breeding group Xenotoca in this second aquarium, some subadults show now the same problem. Food and water-exchanges are the same. - What is very different is that I have a BIG cyanobacteria-problem in the second aquarium (tried changes of water, sand and the like, but don't want to start 100% all over because I want to keep a few of the plants). It is known that cyanobacteria secrete substances which are unhealty for fish. Could these cause deformities?  - As I ruled out the obvious causes of Cyano-growth, I am now poisoning them with Blue Exit, yet another thing to keep an eye on, but the deformities developed before I started poisoning cyano's.