Sweet peas - still furled leaf tips going brown

Not sure if this is a pest, disease or not enough of a specific nutrient, but I have about 90 sweet pea plants, some of which have the most recent (still furled) leaf tips starting to turn brown and die. This is literally the last 1 or 2 millimetres of SOME of the curled leaf tips - when they open the resulting leaf looks okay except for the tips.

Any ideas as to the cause please? I have zero experience with sweet peas, this is my first year of growing them.

Thanks

 

They're in large tubs (with bamboo canes supporting them) filled with a multipurpose compost.

 

Photos ?

 

I'll try and get some later, having a rather hectic day today.

 

The compost is damp but not soggy. We did have a very heavy rain shower a couple of days ago.

Perhaps I shouldn't have used compost due to its ability to hold onto more water?

I've just plunged my hand in deep to a couple of random tubs and the compost is no more than adequately damp, certainly not sodden.

 

Okay, some photos, first two are of still furled leaves:





and here's an affected leaf that has unfurled:

 

I haven't used any fertilizer at all - maybe I need to start using some?

If so, which one? I have some Unwins sweet pea fertilizer (pre-planting) which I forgot to use when I planted them. It's the type that's small granules - I could stick some of that into the compost perhaps?

 

Any more thoughts please anyone? I want to nip this problem in the bud, so to speak.

 

New growth looks fine to me, a few of mine have yellowed or funny tips.. unsteady watering and/ root disturbance maybe?

 

That's just it though, SOME of the new growth looks fine, but some has the brown dead tips.

 

I wouldn't worry too much, how big are they did u pinch them out? I'm sure with 90 plants you'll get flowers just keep an eye for slugs n snails lurking under pot rims ready to munch the bottoms

 

Most of the plants are probably about a foot high now (I planted the seeds (indoors) a little late) - I did pinch them out in one tub (which had rather leggy plants at first) but it made little difference, the others in the remaining tubs aren't pinched out but seem to be growing nice and bushy without my intervention.

Would though still love to know why some of the tips are going brown ......