Why isn't my swimming pool working

My pool is 4 years old- in ground- salt. we swam last summer and water started looking a tad cloudy,  basically never checked the water balance. well about 4 months ago, after a filter cleaning i noticed that the water pressure was still high (at the filter) and my vacuum wasn’t moving at all. checked it (hayward) and made sure there was no debris and noticed that the suction was low. about that time, the motor burned out. so we got a new motor, new salt cell and just today i put in 4 brand new cartridge filters. the pool was already clear of debris before i put in the new filters. but immediately after starting it up, my circulation was still low and my pressure at the filter is still very high- well above what it used to be. we’ve got water features that work fine when on and i double checked the salt cell to ensure that it was clear of any debris. both skimmers are clean.

this problem persists when the water features are OFF.

now there’s a valve that controls the balance between skimmer suction and vacuum suction and i typically have it set to what the pool manufacturer recommended- (60% vac, 40% skim- or vice versa- either way, my problem persists) when i have it at this setting, the vacuum doesn’t move. i literally have to have it at 100% vacuum and then it seems to have full suction. i tick it down like 1 or two clicks and it almost stops moving. when i have it at 100% skimmer, the skimmer is going nuts. at either extreme, the psi at the filter is around 30. after every filter cleaning the pressure used to drop from 30ish back down to 10ish and whenever it got high, that’s when i decided it was time to clean (2-3 months, and we live in arizona where we’d get the occasional wind storm that would gum up the system)

when the system is off, the valve goes back down to zero.

what should i check next? my objective is to drain the pool and refill it within the next week before it gets hot and algae becomes an issue, but if i have a plumbing issue I’d hate to drain and fill and it turns out that something was wrong that required the pool to be empty to fix.

thanks!