I dont think it is relevant to the fish kill but i almost always get suspended algae bloom this time of year as the water temps warm up. It usually dies off after 2-3 weeks.
algae blooms in aquaculture are usually undesirable but the affects are mild. They do cause more PH fluctuation throughout the day and at night time when plants cant photosynthesize the algae can use up/depleate oxygen the fish needs. This is easily countered with aeration.
There can be similar type issues when the algae bloom dies off and starts decomposing.
Its usually a good idea to try to shade your fish tanks and any exposed water to limit algae blooms.
brian
