More often than not, streaks on clothes are caused by undissolved washing powder or residue from detergent. This happens when you’ve loaded too much into your machine so the detergent gets caught in the folds of clothing.
When this is the case; Rub the stains with an ordinary bar of soap, then wash them again in a detergent-free cycle; Soak the cloths in white vinegar for 15 to 30 minutes, then toss back into the washing machine; Use a grease removal solution on the stains.

get it refunded! denim can fade but shouldn’t streak like that

I would have taken them back to the store,that shouldn’t happen!

Wow extremely odd! Was it they way you dried it or was it straight after the wash? Maybe to much washing powder?

No idea, if you washed them like you normally would then the fault is with the manufacturer.

Take them back and ask for a exchange pair. Write a letter to the store and ask for a explanation. let them know how you washed them using what brand of washing powder and if you washed them on their own first. All important to the store owner.

sounds like a manufacturing fault so I would be returning to them to the store

doesn’t sound right – I would have taken them back

I would think that they were faulty and return them.

I would definitely take them back for a refund.

Take them back for sure.

you should get a refund .

there are some good comments here

I doubt this should have happened and would also suggest taking them back to the store.

I’d take them back to the store for a refund.

Returning them is a great idea, if that fails try soaking them in Dylon Black dye for a day then pop on a cold rinse cycle. This should set it.

I had this before. Apparently is the material and quality of the fabric

I agree with what everyone else seems to be saying, if you had not recently used any bleach based products and followed the directions then take them back, the colour may not have been fixed properly.

Take them back where you purchased them from.

Sounds like they may have had contact with bleach from your prior washing load. Have you tried to brush the jeans in case it is a suds build up that happens in some machines.