Help with my brown ale

Recently brewed a brown ale back in October and the flavor never really developed the way I thought it would. Any help and advice would be appreciated.

9 lbs Maris otter
.5 lb victory
.5 lb crystal 60
.5 lb honey malt
.25 lb chocolate malt
.125 lb roasted barley

.75 oz willamette 7.5% aa 60 min
.5 oz east kent goldings 5.7% aa 10 min

Wlp002 English ale yeast

Mash at 154
sparge 4 gallons at 169

The malt in this never really stood out. It just tasted very bland with a hint of chocolate. Did I use too many malts? I forgot to take a fg but I feel like the yeast didn't attenuate well as it was very sweet tasting.

Also, like I mentioned earlier, I brewed this early October and kegged it late November or early December. It developed an off flavor I can't really describe other than trashy and disgusting and kinda soured. I finally just dumped it today. Did I just wait too long to drink on it and it turned or what? Also had 2 other beers that tasted awesome and developed some off flavored after time that were dumped. They were brewed only a week apart from the brown. What's going on here?

Doesn't sound like you waited too long at all. If you have off flavors like "sour," you'll need to re-evaluate your sanitation procedures. No use messing with your recipe until that's under control.

We've never really had sanitation issues before. We rinse everything in pbw. Soak and scrub with a good sponge. Wash with hot water and hose it with some starsan. Am I missing something?

Check your kegging setup... One of the brewers I know had an issue with his brews going sideways after being kegged. He ended up taking his setup apart (especially the liquid side, but don't ignore the gas fittings/lines/etc.), cleaned it all REALLY well, then sanitized the lot of it. Resolved his issue. It's one of the reasons I clean the kegs like I do, as well as the beer lines and faucets.

That might be it then. We clean the inside real well but have never really taken it apart to clean it. Thanks for the advice.

Clean inside the QD's too. You can easily take them apart (notch in the top takes a flat head screwdriver easily), clean and sanitize them. You might find a bit of crud, or something nasty inside one of them. If it's really nasty, I would consider tossing it and replacing the QD... Considering how little they cost, it would be better to KNOW it's safe than to wonder and risk tossing another batch. QD cost is far less than batch cost.