fibre tech falling apart

Feb 27, 2014
Tampa Bay area, Florida
Have Fibretech pool for about 10 years. Last year had rep at house due to trouble with the gelcoat disappearing? Looks like areas that it was fiberglass mat (same shape) disappearing, making it rough and algea to stick to it easily. Rep (of course) told me it was due to chemicals not correct according to their lab...
Now chunks of the bottom are coming off when I brush. Will try pictures. How can this be remedied? Renew the whole surface but NOT fibretech, any suggestions? Ultraguard? Any other surface? IMG_20141227_121702.jpg IMG_20141227_120602.jpg First picture shows bottom with chunk missing, second the chunks