i have an inground 18×36 pool that was originally a gunite pool and is now a fiberglass pool. i keep the chemicals within normal guidelines, but the bottom and sides of the pool looks like it is dirty. when i brush the pool, it really doesn’t help.sometimes when i vacuum,the wheels on the vac head will leave track marks. someone told me it may have to do with the installation of a new heater. is there any way to get rid of this dirty look? the water is perfectly clear.