scratchiness on older lp's

i recently purchased a 1950's set of lp's (ella sings gershwin) and while the records look beautiful for their age, not one visible scratch on any of the 5 records, when they are played there is a lot of scratchiness to them. they have been cleaned in a spin clean. i have only listened to three sides so far. i am wondering if i will be doing any damage to my needle by continuing to listen to this set.
Some folks used a 'horrible' system to 'damp clean' records.
A record brush with fiber nape, and a liquid were popular in the 60's and 70's.
The problem was the fiber and liquid just drove the dirt into the grooves and the combination after a few uses would turn into a hardened noisy horror.

My suggestion is allow the LPs the soak much longer.
Cover the grooves on one side with cleaning fluid with the Lp flat. Let it sit (where the fluid will not evaporate off) for half an hour. THEN reclean in the spin clean. repeat for other side.
Yes it will take longer, but hopefully the grunge locked in the grooves will be removed.

And yes it is bad for your stylus. If i own records with serious noise like that and cannot get them clean, i toss them into the trash.
Wondering how I could accomplish this without soaking the label as well
I have had the same issues with some older classical releases and I just kept cleaning and eventually they got better. I would try what Liz suggests also you might want to try an enzymatic cleaner.

Surface condition does not necessarily reflect the amount of groove damage that may have occurred.

I've heard records that look great but sound terrible and vice versa.

Beauty is only skin deep.
You do not need to get the lable wet at all.
Just allow the LP to lay flat and drip the solution into the grooves. It will stay in the groove area. Just keep it from drying up while soaking
The one point you might get some water on the label is when you pick it up and tilt it to go into the spin clean. Just have a paper towel ready to keep the label dry.
(at least half the labels are actually waterproof, most are somewhat water resistant. only a few really are water, die instantly..)
If it is a buildup in the grooves your stylus should be digging it out. If your stylus stays clean the record is most likely damaged.