My son is 8 months old. he has global developmental delay. hypotonia, fluid retention and other issues. what genetic disorders could be linked to this?

Too many to list...: Speak to your physician, specialists, and geneticist for clearer answers regarding whether they believe your son's issues are related to a genetic disorder.

Many. Standard of: practice in the US is to obtain a Chromosomal microarray, not a chromosome analysis, & a DNA probe for Fragile X. Seek evaluation by a Developmental/Behavioral Pediatrician for genetic & other medical causes of his neurodevelopmental disorder. Also, call your state Early Intervention Program for an assessment of all developmental domains, Physical & Occupational Therapy & other needed therapies.